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TISI ISLANDS PREVENTION USING PSD IMPLANT MASK

IP.com Disclosure Number: IPCOM000009877D
Original Publication Date: 2000-May-01
Included in the Prior Art Database: 2002-Sep-25
Document File: 2 page(s) / 101K

Publishing Venue

Motorola

Related People

Martin Mollat: AUTHOR

Abstract

The incorporation of boron (B) and fluorine (F) into a field oxide region in TiSi based technology leads to an undesirable TiSi formation on the field oxide. Studies show that a BF2 implanted field oxide produces stable TiSi, while n-type or nonimplanted substrates do not. TiSi can be prevented from forming on field oxide by prohibiting BF2 implantation into the PMOS field areas by using a PSD (P+ Source Drain) implant mask as shown in Figure I below.

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MOTOROLA

Technical Developments

TISI ISLANDS PREVENTION USING PSD IMPLANT MASK

by Martin Mollat

The incorporation of boron (B) and fluorine (F) into a field oxide region in TiSi based technology leads to an undesirable TiSi formation on the field oxide. Studies show that a BF2 implanted field oxide produces stable TiSi, while n-type or nonimplanted substrates do not. TiSi can be prevented from forming on field oxide by prohibiting BF2 implantation into the PMOS field areas by using a PSD (P+ Source Drain) implant mask as shown in Figure I below.

BF2 Implant

1 1

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i i

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1

1 eI PMOS /

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Fig. 1 Diagram showing a PSD implant mask on PMOS field area.

The solubility of oxygen in TiSi reactions prohibits the formation of TiSi2 since oxygen tends to snowplow at the growing Ti/Si interface. As the concentration of oxygen increases, the formation of Ti3Sis incorporates even more oxygen. This intennediate layer is later converted to TiSi2. C49 phase TiSi2 interface is driven by small free energy changes, and is sensitive to temperature, stress, nucleation sites.

The BF2 implant introduces a high concentration of fluorine into the oxide which does not anneal out, causing lattice strain. In addition, the presence of

Motorola. Inc. 2000

boron in the oxide facilitates fonnation of oxygen vacancies through substitution of boron for silicon sites in the lattice, leading to a silicon rich film. In contrast, Phosphoro...